1. Field of the Invention
This invention relates to an apparatus for monitoring an area adjacent to a vehicle such as an area in front of the vehicle. In addition, this invention relates to a computer program for monitoring an area adjacent to a vehicle.
2. Description of the Related Art
A known on-vehicle apparatus takes an image of conditions of a road in front of a subject vehicle, and analyzes the image to detect an obstacle to the subject vehicle. Typical operation of the known on-vehicle apparatus is as follows. A preceding vehicle with respect to the subject vehicle is detected. The positional relation between the preceding vehicle and the subject vehicle is detected. On the basis of the detected positional relation, a decision is made as to whether or not the preceding vehicle is an obstacle to the subject vehicle. When it is decided that the preceding vehicle is an obstacle, the speed of the subject vehicle is controlled or an alarm is given. To detect a preceding vehicle and accurately measure the position thereof, the known on-vehicle apparatus implements complicated image and signal processing procedures.
U.S. Pat. No. 5,369,590 corresponding to Japanese patent application publication number 5-296767 discloses an inter-vehicle distance detecting device which operates as follows. The device displays the images of preceding vehicles, sets a tracking window surrounding one of the images and tracks it, calculates the distance from the driving vehicle to the preceding vehicle, and sets a plurality of shadow windows which are not displayed and which are different from the tracking window, at predetermined positions in the image taken by one of top and bottom image sensors. Distances from the driving vehicle to objects caught by the respective shadow windows are detected from the deviation between top and bottom corresponding image signals, and a symmetry determining means reads image signals in an arbitrary domain in the shadow windows and surroundings and determines horizontal symmetry. A cut-in vehicle or lane change of the one of the preceding vehicles which is image-tracked by predicting movements thereof in front of the driving vehicle is detected based on information about the distances from the driving vehicle to the objects in the shadow windows, an output of the symmetry determining means, and information provided by a calculation based on the preceding vehicle tracked by the tracking window.
Japanese patent application publication number 9-223235 discloses a system mounted on a subject vehicle. The system includes a camera for taking an image of a road in front of the subject vehicle. On the basis of the road image, detection is given of the boundary between the lane where the subject vehicle is moving and a lane next to the lane of the subject vehicle. A vehicle moving in the next lane and preceding the subject vehicle is recognized in response to the road image. Moving conditions of the next-lane preceding vehicle are detected. The detected lane boundary and the detected moving conditions are used in detecting the inclination angle of the moving direction of the next-lane preceding vehicle relative to the lane boundary. The system decides whether or not the next-lane preceding vehicle will enter the lane of the subject vehicle on the basis of the detected inclination angle.
Japanese patent application publication number 11-48885 discloses an on-vehicle distance measurement apparatus including two juxtaposed cameras for taking images of an area in front of a subject vehicle. The cameras have image sensors onto which the images are focused by optical systems, respectively. The images on the image sensors are compared by electrical image processing to get a condition where they best correlate with each other. Under the best-correlation condition, shifts of a same object in the images from the optical axes are detected. The distance from the subject vehicle to the object is measured by triangulation responsive to the detected shifts. A plurality of objects such as vehicles preceding the subject vehicle can be detected. In the case where first and second preceding vehicles are detected and the first preceding vehicle is handled as a distance-measured object, a decision is made as to whether or not the second preceding vehicle has entered the region between the subject vehicle and the first preceding vehicle. Also, a decision is made as to whether or not the first preceding vehicle has moved from the region between the subject vehicle and the second preceding vehicle to a lane different from the lane of the subject vehicle. When it is decided that the second preceding vehicle has entered the region between the subject vehicle and the first preceding vehicle, the distance-measured object is changed from the first preceding vehicle to the second preceding vehicle. When it is decided that the first preceding vehicle has moved from the region between the subject vehicle and the second preceding vehicle, the distance-measured object is changed from the first preceding vehicle to the second preceding vehicle.
It is a first object of this invention to provide a simple apparatus for monitoring an area adjacent to a vehicle.
It is a second object of this invention to provide a simple computer program for monitoring an area adjacent to a vehicle.
A first aspect of this invention provides an apparatus for monitoring an area adjacent to a subject vehicle. The apparatus comprises image taking means for taking an image of an area at and around a place to which the subject vehicle is directed; predicting means for predicting a region to which the subject vehicle will travel, the predicted region having a left-hand boundary and a right-hand boundary; setting means for setting a detection area near at least one of the left-hand boundary and the right-hand boundary of the predicted region, the detection area extending along a direction of travel of the subject vehicle; and deciding means for deciding whether or not a three-dimensional object exists in the detection area in response to the image taken by the image taking means.
A second aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the detection area comprises small areas having a prescribed width, and the small areas are arranged along the direction of travel of the subject vehicle, and are partially overlapped to enhance a resolution relating to distance from the subject vehicle.
A third aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the predicting means comprises means for setting the predicted region in response to a width of the subject vehicle.
A fourth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the predicting means comprises turn condition detecting means for detecting a turn condition of the subject vehicle, and means for setting the predicted region in response to the turn condition detected by the turn condition detecting means.
A fifth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the predicting means comprises lane mark detecting means for detecting lane marks on a road along which the subject vehicle is traveling, and means for setting the predicted region in response to the lane marks detected by the lane mark detecting means.
A sixth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the setting means comprises vehicle speed detecting means for detecting a speed of the subject vehicle, and means for setting the detection area in response to the speed detected by the vehicle speed detecting means.
A seventh aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the image taking means comprises a plurality of cameras spaced at a prescribed interval, and the deciding means comprises means for detecting a parallax between portions of images taken by the cameras which correspond to a same object in the detection area, means for measuring a distance to the same object from the detected parallax, means for determining whether or not the measured distance to the same object is shorter than a distance to a corresponding road surface, and means for deciding that a three-dimensional object exists in the detection area when it is determined that the measured distance to the same object is shorter than the distance to the corresponding road surface.
An eighth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the detection area is at a prescribed distance or shorter from the subject vehicle for detection of a cut-in vehicle with respect to the subject vehicle.
A ninth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the predicting means comprises means for setting the predicted region in response to a width of the subject vehicle, wherein the setting means comprises means for setting detection areas near the left-hand boundary and the right-hand boundary of the predicted region, and the detection areas extend along the direction of travel of the subject vehicle, and wherein the deciding means comprises means for deciding whether or not the subject vehicle can pass through a narrowed road zone in response to portions of the image which correspond to the detection areas.
A tenth aspect of this invention is based on the first aspect thereof, and provides an apparatus wherein the predicting means comprises means for setting the predicted region in response to a width of the subject vehicle, wherein the setting means comprises means for setting detection areas near the left-hand boundary and the right-hand boundary of the predicted region, and the detection areas extend along the direction of travel of the subject vehicle, and wherein the deciding means comprises means for deciding whether or not the subject vehicle can be successfully parked into a limited space in response to portions of the image which correspond to the detection areas.
An eleventh aspect of this invention is based on the ninth aspect thereof, and provides an apparatus wherein the predicting means comprises means for setting the predicted region in response to a length of the subject vehicle.
A twelfth aspect of this invention is based on the first aspect thereof, and provides an apparatus further comprising notifying means for notifying a result of the deciding by the deciding means.
A thirteenth aspect of this invention is based on the eighth aspect thereof, and provides an apparatus further comprising an on-vehicle system for implementing at least one of (1) inter-vehicle control of the subject vehicle and (2) an inter-vehicle warning process for a preceding vehicle with respect to the subject vehicle; warning means for generating an alarm for a cut-in vehicle in response to a result of the deciding by the deciding means; and preventing means for preventing the warning means from generating a second alarm during a prescribed time interval from a moment of generation of a first alarm.
A fourteenth aspect of this invention is based on the thirteenth aspect thereof, and provides an apparatus wherein the preventing means comprises means for, in cases where a cut-in vehicle is handled as a preceding vehicle by the on-vehicle system, preventing the warning means from generating an alarm.
A fifteenth aspect of this invention provides a computer program for operating a computer as the apparatus of the first aspect of this invention.